Gas tube ionizer and process



March 3, 1953 w, A. E AN 2,630,550

GAS TUBE IONIZER AND PROCESS Filed March 20, 1948 2 SHEETS--SHEET 1 25 jig-J 5 +5sov Z0 INVENTOR W A GEOHEGAN GAS TUBE IONIZER AND PROCESS Filed March 20, 1948 March 3, 1953 Patented Mar. 3, 1953 UNITED STATES PATENT OFFICE GAS TUBE IONIZER AND PROCESS William Anthony Geohegan, Larchmont, N. Y.

Application March 20, 1948, Serial No. 15,995

6 Claims. (01. 315-201) The present invention relates to processes of ionizing gas filled electronic tubes and to ionizers for the same.

A purpose of my invention is to render the re sponse from gas filled tubes uniform and avoid delay or difiiculty in striking which is likely to occur when a considerable interval has elapsed since the tube was last struck.

A further purpose is to maintain a gas filled tube in a partially ionized condition during an.

inactive period without causing such tube to strike during the inactive period and without creating any false condition of conductivity which Would influence other parts of the circuit.

. In a counting circuit employing gas filled tubes as operating units, a further purpose is to make each unit respond to a counting impulse having the shortest possible duration.

A further purpose is to predispose a gas filled tube to more rapid ionization incident to application to the tube of a striking pulse.

A further purpose is to interpose in circuit with each electrode of a gas filled tube an alternating voltage applied through a reactance, preferably a series capacity.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the embodiments in which my invention may appear, choosing the forms shown from the standpoints of convenience in illustration, satisfactory operation and clear demonstration of the principles involved.

Figure 1 is a circuit diagram useful in explaining the invention as applied to a standard gas filled tube of the conventional neon or argon type.

Figure 2 is a circuit diagram showing the application of the invention to a plurality of gas filled tubes in any suitable circuit arrangement.

Figure 3 is a circuit diagram showing the invention employing. a. direct current source applied to a gasfilled tube having an auxiliary electrode.

. Figures 4 and 5 are circuit diagrams showingforms using auxiliary electrodes connected to alternating current sources.

Figure 6 is a conventionalized illustration of a plurality of counting rings or decades to which the invention has been applied.

Figure 7 is a more detailed diagrammatic circuit diagram of a suitable counting ring or decade employing the principles of the invention.

In the drawings like numerals refer to like parts throughout.

In accordance with the principles outlined in my copending U. S. Patent Application 662,038, filed April 13, 1946, for Electronic Counter and Process, there are many advantages in employing gas filled tubes such as the conventional neon and argon tubes, as operating units in counting rings or decades, and also desirably as indicators of the count. In the operation of counting rings according to my prior invention above referred to, it has been found that maximum counting speed is limited by the speed of ionization of the gas filled tubes at the striking voltage applied by the counting ring. There may therefore be an undesirable and somewhat unpredictable variable limitation imposed on the maximum counting speed after a particular unit or units of the counting ring have been inactive for an extended period, which may in'some cases be as little as one hour. It has therefore been necessary in some cases to make a precounting run in order to be certain that all gas filled tubes have recently been fully ionized, immediately before an important test.

This expedient however does not solve the difficulty when the total count involves periods of relative inactivity and the final count is not completed in a short interval of time, as individual gas filled tubes are likely to have been inactive for an extended period before they receive the next counting impulse.

In numerous other applications of gas filled tubes, this same characteristic is evident, and wherever it is important in gas filled tubes to have a minimum time response under a. striking impulse, the difliculty above noted is encountered.

I have discovered that it is possible to maintain gas filled tubes continuously, or intermittently with a short delay between impulses, in a partially ionized condition which will avoid any tendency for false operation due "to unintended complete ionization and will nevertheless constantly assure the presence of an adequate supply of ions to permit rapid striking of the tube when desired.

Thus there is no tendency of the partial ionizing current to influence the striking of the tube, except to predispose the tube for striking in the shortest possible time.

It is important of course that there be a limiting impedance in the circuit of the partially ionizing current which will assure that the current caused to flow between the ionizing electrode and the main electrodes will not interfere by causing striking of the gas filled tube. The

micromicrofarad. Flgure the capacitance 23 introduced by the cases with alternating current, the tube will be modified to the extent of including an internal partially ionizing electrode in addition to the conventional electrodes.

The tube in its inactive or nonstriking condition may not be under any voltagebetween the main electrodes or may be subjected to a voltage less than the striking voltage applied inany'suitable way from a circuit whose details are unimportant for the present purpose, and typically illustrated as including a resistor 23 on the positive side, the other terminal being grounded at 24. This applied voltage if any is not only below the striking voltage but also below a voltage which would maintain ionization in the gas filled tube. A tube of this character is likely to strike on a voltage of the order of 60 or 80 volts, and will remain struck at about 50 volts.

In order to maintain the gas filled tubeconstantly in a partially ionized condition, metallic conducting partially ionizing electrode 25 is ap- 'plied, conveniently adjacent the outside of the envelope, and connected to a suitable source, in this instance an alternating current preferably of the order of 350 volts. Of course this voltage may bevaried if desired. The voltage applied to the electrode 25 is maintained at a sufiiciently high level so that partial ionization occurs in the gas filled tube, and the capacitance between the ionizing electrode 25 and the main electrodes of the tube is low enough so that the iOIllZiIlg current is not sufiicient to cause an appreciable effect on the voltage in the main circuit. Thus the effect of the partially ionizing electrode is to predispose the gas filled tube to rapid ionization as soon as a striking impulse'is applied.

The circuit illustrated'in Figure 1 can readily partially ionizing electrodes has been changed,

such electrodes being indicated as bands or wires adjacent the outsides of the envelopes of the tubes.

If desired, a partially ionizing electrode 25 can be incorporated in the gas filled tube itself as I shown in Figures 3, 4 and 5. As indicated in Figure 3, a direct current is applied to the internal partially ionizing electrode25 through a current limiting series resistor 27 which may for example be of the order of magnitude of 3,008 megohms Where the voltage applied is 350 volts.

With the alternating current form of partial ionization, the limiting impedance may take the form of series resistance 28 in Figure 4:, which with a partial ionization voltage of 350 volts at commercial frequency (usually 60 cycles) should be of the order of 3,000 megohms, or series capacitance 29 in Figure 5 which may uith the voltage and frequency suggested suitably be about i It will be understood that in 'to the partial ionizing electrodes.

capacitor there shown will function exactly as the capacitance introduced from the external electrodes 25, 25 and 25 in Figures 1 and 2.

Where the invention is to be applied to counting rings or decades using gas filled tubes as operating elements, the arrangement shown in Figure 6 is convenient. In this form successive decades 3| and 32 consisting of gas filled tubes 20 arranged in a suitable counting circuit (for example as later described) and suitably having 10 units in each counting ring, are externally maintained in partial ionization by wires or loops '33 and 34 passing adjacent to the envelope of eac'htu'be and connected, conveniently in parallel, to a suitable source of partial ionizing voltage, in this "case an alternating current voltage of 350 volts at commercial frequency. The current limiting capacitance is here applied as in Figures 1 and 2 due to the gap between the external partial ionizing electrode and the main internal electrodes of the tube.

The partial ionizing voltage can be"applied"directly but since it is likely to be a moderately high voltage it is wise for the sake of safety to apply from the secondary of a high voltage transformer 35 through a, current limiting resistor '36 In order to prevent coupling between decades athigh-irequency it is wise to employ a 'highfrequency ground suitably through condenser 37. The magnitude of the current limiting resistor 36may-be oi'the order of 0.5 megohm where the secondary voltage on the transformer is of the order of 350 volts at 60'cycles alternating current, and the capacitor 37 may be'of the order of 0.0001-microfarad.

A suitable form of counting ring ordecade-in which the invention'may be applied is shown in Figure 7.

In the accompanying drawings, certain "electronic tubes and impedances are ill-ustrate'd,'and in several cases, to aid the user, I have given examples of tube types and impedance dimen- 'sions. It will be understood that these are stated in illustration but not in limitation, and that changes and readjustments in tube types and impedance dimensions may readily beniade by those skilled in the art without departing from the spirit of the disclosure.

Figure 7 illustrates a counting ring, whichin this case is a decade, consisting of ten unitsnumbered respectively from 0- to 9 inclusive. Each unitconsists of its electronic elements and associated impedances, constituting an operative unit to receive, respond to and usually indicate'the counting impulse, and pass along the succeeding impulse to tne next similar unit. It will be evident that this is truly a ring in the sense that not only doesnumber follow number 0,'etc., but also number 0 follows number 9.

It will be evident that auxiliary effects may occur when the ring completes a cycle, such "as the actuation or advance of another counting ring, but the discussion of such features is omitted herein as it'bears no I relation to the present invention. It will also be understood that means maybe provided-for resetting the counting ring to 0, but such subject matter The individual gas tubes in the individual units are indicated at 40 to 49 inclusive, the terminals 50 of the gas tubes being suitably identical and capable of connection with either side of the tube on the high voltage side. Also employed in each unit is an individual amplifier to 60, inclusive, which in the particular embodiment shown is a triode having a cathode 6|, anode 62 and control grid 63. For convenience, twin triodes such as 6J6 or 7F? are shown in which two amplifiers are placed in a single envelope, but it will be evident that this may not in all cases be necessary or desirable. It will further be evident that while I have shown triodes, other tube constructions, such as pentodes may be employed.

For convenience the cathode heater and heater circuits which will be used have been omitted from the drawing.

Energy actuation of the units is accomplished by a direct current source having its positive side above ground connected at 64 and its negative side at ground connected at 65. The lead 64 provides positive voltage connection to all units of the ring and is connected to all anodes 62 through suitable substantially equal anode load resistors 66, one in each unit of the ring. Without attempting to limit to a particular value, it may be stated that good results have been obtained using an applied voltage of approximately 350 volts and a resistance of approximately 0.24 megohm in the anode load resistors.

The cathodes (H are connected together at 61 and connected to ground through the cathode bia resistor 68, which in the preferred embodiment of my invention may have a resistance of approximately 500 ohms.

In each unit, the gas tube is connected at B9 to the anode of the amplifier of that unit, thus applying the higher voltage to the terminal of the gas tube to which this connection 69 is made. It will be noted that elsewhere this terminal will be referred to as the higher voltage terminal of the gas tube.

The lower voltage terminal of each gas tube is connected at 10 to ground through one of the preferably substantially equal resistors H, which in the preferred embodiment desirably has a resistance of approximately 0.24 megohm. The lower voltage terminal of each device having sharp cut-off (gas tube) is also connected through one of the preferably substantially equal resistors 12 to the control grid of the amplifier of each other unit in the ring, but not to the amplifier of the unit containing the particular gas tube. In the number 0 unit these individual resistors are designated I2 I2 I2 to 12*, inclusive, and it will be understood that in each other unit there will be an individual resistor between the lower voltage terminal of the gas tube or other device having harp cut-off and the control grid of each amplifier other than the amplifier in that unit.

For best results the resistors 12 should be substantially equal and should have in the preferred embodiment a resistance of approximately 4.7 megohms.

Between the lower voltage terminal of each gas tube and the control grid of the next amplifier in the sequence of counting, I also interpose in series connection a resistor 13, preferably having a resistance of approximately 2.2 megohms, and a capacitor 14, preferably having a capacity of approximately 100 micro-microfarads.

The impulse to be counted, which may of course be transmitted from a preceding counting ring or from a suitable impulse circuit, will be received at the terminal 15 and transmitted through individual resistors 16, suitably each having in the preferred embodiment resistances of about 4.7 megohms, to the individual control grids of the amplifiers of each unit in the ring. The input terminal 15 is also connected to ground through a resistor 17 preferably having a value of approximately 0.51 megohm.

It will be understood that with reasonable matching, the values of the impedances mentioned can be varied widely, and that the particular values given are stated for convenience of those who may construct the device and because the values given fit in with standard resistance size which are available on the market.

It will be understood that impulses of widely variant character may be counted, provided they are passed through a suitable input circuit which will convert them to nearly uniform impulses to be applied at the terminal 15. It will also be understood that as well known in the art, means may be used to amplify and shape the pulses to the most advantageous form for counting in the ring. It will also be evident that the original impulses may be used to trigger impulses of the preferred character for counting. All impulses received by the counting ring will be positive and preferably of about 0.1 millisecond duration, and preferably of the order of volts in amplitude. The decade will function to count such impulses with a. high degree of accuracy, and at speeds as high as about 1000 per second with the particular impedance values given.

The amplifiers and gas tubes operatively interconnected as shown in Figure 7 with the impedances illustrated, form a system such that in a stable state at least one gas tube will be conducting (striking or lighted), whereas no more than one can be conducting at a given time.

If none of the devices having sharp cut-offs were conducting, all of the control rids would be at approximately zero or ground potential, all of the anodes would be regulated by the cathode bias resistor 68 to a voltage of approximately volts in the example given, and all of the gas tubes would tend to become conducting (strike). When the device is first turned on, and before any impulse to be counted arrives, the conducting tube may be any one of the ten. The counting ring may then be set to zero by suitable means. As soon as one of these gas tubes becomes conducting (strikes) the current flowing through it develops a positive voltage at its lower voltage terminal 10 and applies this voltage through one of the resistors 12 to the control grid of each amplifier in the other units, but not to the amplifier in its own unit. This positive voltage applied to the control grids of the other amplifiers causes all of such amplifiers to draw more current and lowers the voltage applied across each of the other gas tubes to a value below the voltage which will maintain conduction, thus preventing the gas tubes from striking. At the same time it will be evident that the potential of the control grid of the amplifier in the unit having the conductin gas tube will be very slightly influenced, since there is no resistor connecting this gas tube to the control grid of its own amplifier. At equilibrium, therefore, a condition will be reached in which only one gas tube will be conducting.

Usin the example shown, and assuming that the gas tube in unit number 0 has struck, typidrive all anodes ina'negative direction.

volts to about 2 volts). 7

positive voltage applied through the resistors 12 from the lead T0 at the lower voltage terminal iaiesogtso '"ca1 values for 'the'voltagesof the elements under the preferred conditions "would be J as follows:

For the anode of'amplifiermumbed 0 about --120volts; I V s For thelower'voltage terminal of the-gas tube of unit number 0 approximately-60 volts;

For the control grid of amplifier number 0;

approximately --2 volts;

For all other control grids, approximately For all cathodes, approximately 6 volts.

It will be understood that these-and 'other values given are not intended to *limit to the particular values, but "merely -'to serve asex- "amples.

I Since the systemis "perfectly symmetricalfit will be understood that it will have ten stable states, or one corresponding to'each-unit inthe ring, if the numbero'funits is other than ten. In each'one'ofthese-stable states oneof the gas tubes will be lit.

Assuming that-unit number 0 isoperating and .gas tube number 0 "is lit, and'that the interval'since the last count has'been sufficient to permit all capacitors substantially to reach equilibrium, and that "a new input impulse is applied to input terminal 15, it will be evident that this'impulse will'be transmitted through resistors 16 to the control grids ofall of the amplifiers in the ring; tendingto drive all control grids in" a'positive direction and tending to The anode of the amplifier (triode) number 0 is driven to a much lowervoltage (possiblyof the order of 35 volts),and the gas tube 'orother-similar device in unit number 0 ceases to conduct, while the lower voltage side' of this gas tube drops very sharply" in voltage (from'approximately '60 The removal of "this at lead Til, transmitted inthis way to this con- 'trol grid, more-than o'iTsets "the positive change 'dueto the input impulse, sothat the net effect upon the control grid of "the amplifiermfxunit number 1 is negative, its anode'risesto a. high voltage (possibly of the order of'150 volts) and causes conduction of the device having-sharp cut-01f (gas tube) in unit number 51.

It will thus be seen that the input impulse is amplified andinverted by the amplifier :of unit number 0 in the way characteristic :of vacuum tube amplifiers and that this amplified-impulse is transmitted-through the gas tube of unit number 0 and through the resistor I3 and-capacitor M in series to the control grid of the amplifier in unit number 1. Forbest results the .time

constant of the resistor T3aridicapacitor14 is long as compared with thedurationof the input impulse, although voperationispossible with a time constantequal to or slightly shorter than the duration of this impulse. Because ofuthis time constant relation, the voltage transmitted in this way is effective. until after the termination ofthe'input impulse. The current flowing" :through *the .lamp in unit number '1 is then e'fiective' as previously-described to hold the'volt- 'age 'of *allother *gas tubes 'below the striking voltage, causing -thegas tube in unit number 0 toextinguish,and'all other gas-tubes in the remaining units to remainextinguished.

It is required for operation of the device-that 'the' intervalbetween impulses be sufiioient so that all condensors cansubstantially" reach equilibrium con'ditionbefore'the arrival of the next impulse. "The successive impulsesthen' function in the same "wayto transfer the condition of conduction or --str-iking from one-gas'tubeorsimilar device to the next in the order of the count as predetermined by the connection between-the lower-volt- =ageterminal of'each gas'tube and the control grid of the next amplifier through the resistance and capacitor in series. When the-sequenceLof operaitions 'has lcaused .conduction .of gas tube 49 in innit-number $93 the next succeeding impulse to .be counted will actuate unit number fO .in ex- -actly the same manneras the count is trans- .ferred fromianyoneLof thepreViOus units to the next unit of. the ring.

It will .beievidentithat at any position, the count in the particular 'decadewill be indicated bythe lighting of a particularxgastube, and that, where desired, if some other devicehaving sharp cutoff be 'used instead of argas tube-the particular decade may beprovided' with other indicatin means, or with a gas tube usedpurely asian indicator, .or where indicationl'is not required, this vfunction may be dispensed with.

The partial ionizing-terminaltiixaszshown in Figure '7 willpreferably be connected toxthe partial ionizing source in the. manner showninFig- .In operation it will be understood that whena ,gasfided tube. 20 or i 26 .is .--a.:nonstriking; condition without any partial ionizing-current, ,asfor example whereastandard neon tube is under an impressed voltage of the order of 30 volts, substantial time (probably of the order of .2 milliseconds-at thevoltages used) will elapse before a striking impulse of suitableorderof magnitude (for examplefiflo volts) can establish ionization in thetub e. This is an appreciable time interval in very high velocity counting-and other functions .in whichgas filled-tubes are employeda-s insome cases itis desirable to count impulses recurrently atintervals of less than 1 microsecond.

I-naccordance with thepresent invention, the

ionizing electrode maintains a constant condition of partial-.-ionization which .cuts the timelag on striking of a gas filled: tube to less than onetenth of a millisecond. This greatly increases the maximum counting speed attainable. ,Since an impedance isapplied to the, partial ionizing voltage,the current built .up in the main circuit due to. the partial ionization ofthegas filled tube should never attain-a substantial value :Which could interfere with main circuitoperation. In the direoticurrent formthe-current due to'the ...par tial ionization is limited by resistancewherevas in ,v the alternating current-formally form of impedance may be employed, the mostrconvenient .in many cases being the capacitance inherently -occurring between-the partial ionizing electrode and the normal electrodes =When-the ionizingelec- .trode is'on the outsideof the envelope.

Where thetube envelope is made of a conductingmateriaI suohas-metal, theuseof an external partial ionizing electrode will'be. restricted to 111086021895--Where,the. envelope .is .well insulated .fromground and from all .of .the tubev elements.

In suchcases, where'it'is well insulated, either 9 an external electrode may be used, or the envelope itself may be used as a partial ionizing electrode.

It will be evident that in general, the voltage from the partially ionizing source will greatly exceed the striking voltage of the tube to insure that some ionization occurs, but because of the fact that it is applied through a high impedance, the current it produces is too low to affect adversely the voltages on the main electrodes, and since the voltage across the main electrodes is insuflicient to maintain ionization, the tube will not strike. In the cases of the values illustrated, the partial ionizing current will be less than 1 microampere. It may be desirable in some cases to use a somewhat higher partially ionizing current, for example of the order of 10 microamperes or higher, and this can be done particularly where low impedance circuits supply the main electrodes.

It will be understood that in some counting circuits the gas filled tube is employed merely as an indicator, and in such cases there is no need for partial ionization in accordance with this invention. The invention finds its use where the gas filled tube performs a function in the operation of the circuit.

All of the values of impedances mentioned are based on 60 cycles in the case of alternating current, and they will of course vary with frequency.

In view of my invention and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the process or structure shown, and I therefore claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In an electronic counter, a counting ring having units operatively interconnected and in cluding in combination an amplifier in each unit, a gas filled tube in each unit, means in each unit put in operation by the amplifier and the conduction of the gas filled tube in that unit for preventing each other gas filled tube in the other units from conducting at the same time, a partial ionizing electrode for each gas filled tube external to the tube and adjacent the same, a

source of partial ionizing voltage for the partial i ionizing electrodes and connected to the partial ionizing electrodes, and impedance means for limiting current flow through the partial ionizing electrodes.

2. In an electronic counting ring, a plurality of units operatively interconnected, having an amplifier provided with an anode, a cathode and a control grid in each unit, a gas tube in each unit interposed in the circuit between the output of each amplifier and the control grid of every other amplifier except that amplifier, means including each of the gas tubes when it is conducting for feeding of voltage from the amplifiers of each one of the units to each other unit for rendering the gas tubes in the other units non-conducting, means including unit transfer impedance for transferring an impulse from the amplifier of one unit to the amplifier of the next unit, a partial ionizing electrode in operative relation to each gas tube, a source of partial ionizing voltage for the partial ionizing electrodes and connected to the partial ionizing electrodes and impedance means for limiting current flow through the partial ionizing electrodes.

3. In an electronic counting ring, a plurality 10 of units operatively interconnected, having an amplifier provided with an anode, a cathode and a control grid in each unit, a gas tube in each unit interposed in the circuit between the output of each amplifier and the control grid of every other amplifier except that amplifier, means including each of the gas tubes when it is conducting for feeding of voltage from the amplifiers of each one of the units to each other unit for rendering the gas tubes in the other units non-conducting, means including unit transfer impedance for transferring an impulse from the amplifier of one unit to the amplifier of the next unit, a partial ionizing electrode in operative relation to each gas tube, a source of partial ionizing direct current voltage for the partial ionizing electrodes and connected tothe partial ionizing electrodes, and resistance means for limiting current flow through the partial ionizing electrodes.

4. In an electronic counting ring, a plurality of units operatively interconnected, having an amplifier provided with an anode, a cathode and a control grid in each unit, a gas tube in each unit interposed in the circuit between the output of each amplifier and the control grid of every other amplifier except that amplifier, means including each of the gas tubes when it'is conducting for feeding of voltage from the amplifiers of each one of the units to each other unit for rendering the gas tubes in the other units non-conducting. means including unit transfer impedance for transferring an impulse from the amplifier of one unit to the amplifier of the next unit, a partial ionizing electrode in operative relation to each gas tube, a source of partial ionizing alternating current voltage for the partial ionizing electrodes and connected to the partial ionizing electrodes, and impedance means for limiting current flow through the partial ionizing electrodes.

5. In an electronic counting ring, a plurality of units operatively interconnected, having an amplifier provided with an anode, a cathode and a control grid in each unit, a gas tube in each unit interposed in the circuit between the output of each amplifier and the control grid of every other amplifier except that amplifier, means including each of the gas tubes when it is conducting for feeding of voltage from the amplifiers of each one of the units to each other unit for rendering the gas tubes in the other units non-conducting, means including unit transfer impedance for transferring an impulse from the amplifier of one unit to the amplifier of the next unit, a partial ionizing electrode in operative relation to each gas tube, a source of partial ionizing alternating current voltage for the partial ionizing electrodes and connected to the partial ionizing electrodes and capacitance means for limiting current flow through the partial ionizing electrodes.

6. In an electronic counting ring, a plurality of units operatively interconnected, having an amplifier provided with an anode, a cathode and a control grid in each unit, a gas tube in each unit interposed in the circuit between the output of each amplifier and the control grid of every other amplifier except that amplifier, means including each of the gas tubes when it is conducting for feeding of voltage from the amplifiers of each one of the units to each other unit for rendering the gas tubes in the other units non-conducting, means including unit transfer impedance for transferring an impulse from the 1:1: amplifier of one unit. to the; amplifier, of: the: next unit, a, partial ionizingelectrodeivini operativei relation. to each gas tube, a; source: of par-,- tial ionizing alternating current voltage for the partial ionizing electrodes and connected to the partial ionizing electrodes. and resistance. means for. limiting current flow through; the partial ionizing electrodes.v

WILLIAM; ANTHONY: GEOHEGAN REFERENCES. CITED.

The; following references: are; of record the Number Date;

Schmierer J an.. 10'. 1933 Name Date Qstermeier Jan. 14, 1936- Swart Oct. 26, 1937, Langer -Aug. 12, 1941 Hall. Apr. 28, 1942 Blount Nov. 24, 1942 Massonneau June 26, 1945 Colman Mar. 5, 1946 Compton June 18, 1946 Dickinson July 2, 1946 Stutsman June 21, 1949 Edgertoni Aug, 16, 1949 

